U.S. patent application number 16/373190 was filed with the patent office on 2019-10-10 for controller for machine tool.
This patent application is currently assigned to FANUC CORPORATION. The applicant listed for this patent is FANUC CORPORATION. Invention is credited to Naoto SONODA, Kenta YAMAMOTO.
Application Number | 20190310602 16/373190 |
Document ID | / |
Family ID | 67991575 |
Filed Date | 2019-10-10 |
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United States Patent
Application |
20190310602 |
Kind Code |
A1 |
YAMAMOTO; Kenta ; et
al. |
October 10, 2019 |
CONTROLLER FOR MACHINE TOOL
Abstract
To provide a numerical controller for a machine tool capable of
shredding chips efficiently along one path by making oscillating
motion involving synchronization between multiple axes and
intermittently making cutting-out motion and cutting-in motion. A
controller is for a machine tool used for thread cutting of a work
as a target of the thread cutting using multiple axes, comprising:
a movement command generation unit that generates a movement
command for the multiple axes; an oscillation command generation
unit that generates an oscillation command for causing a work
rotary axis, a tool feed axis, and a radial direction motion axis
to make oscillating motion involving synchronization between these
three axes, the oscillation command being for causing a cutting
tool to make motion of departing from the work while making
cutting-out motion on the work and make cutting-in motion on the
work intermittently; and an adder that adds the movement command
and the oscillation command and outputs a total movement command
resulting from the addition.
Inventors: |
YAMAMOTO; Kenta; (Yamanashi,
JP) ; SONODA; Naoto; (Yamanashi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FANUC CORPORATION |
Yamanashi |
|
JP |
|
|
Assignee: |
FANUC CORPORATION
Yamanashi
JP
|
Family ID: |
67991575 |
Appl. No.: |
16/373190 |
Filed: |
April 2, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05B 19/186 20130101;
G05B 2219/49314 20130101; G05B 2219/36198 20130101; G05B 2219/49047
20130101 |
International
Class: |
G05B 19/18 20060101
G05B019/18 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 6, 2018 |
JP |
2018-073721 |
Claims
1. A controller for a machine tool used for thread cutting of a
work as a target of the thread cutting using multiple axes,
comprising: a movement command generation unit that generates a
movement command for the multiple axes; an oscillation command
generation unit that generates an oscillation command for causing
three axes including at least a work rotary axis, a tool feed axis,
and a radial direction motion axis to make oscillating motion
involving synchronization between the three axes including at least
the work rotary axis, the tool feed axis, and the radial direction
motion axis, the oscillation command being for causing a cutting
tool for the thread cutting of the work to make motion of departing
from the work while making cutting-out motion on the work and make
cutting-in motion on the work intermittently; and an adder that
adds the movement command and the oscillation command and outputs a
total movement command resulting from the addition, wherein the
total movement command is output to the machine tool.
2. The controller for the machine tool according to claim 1,
wherein the oscillating motion is an arc motion, and the
oscillation command is an arc command.
3. The controller for the machine tool according to claim 1,
wherein the oscillation command generation unit generates the
oscillation command for making the intermittent motions at a
predetermined cycle.
4. The controller for the machine tool according to claim 3,
wherein the predetermined cycle is synchronized with the work
rotary axis.
5. The controller for the machine tool according to claim 3,
wherein the predetermined cycle is a set optional temporal
cycle.
6. The controller for the machine tool according to claim 3,
wherein the predetermined cycle is defined by an external signal.
Description
[0001] This application is based on and claims the benefit of
priority from Japanese Patent Application No. 2018-073721, filed on
6 Apr. 2018, the content of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a controller for a machine
tool used for thread cutting by means of coordinated motion of
multiple axes during the thread cutting. The present invention
particularly relates to a controller for a machine tool capable of
shredding chips occurring during thread cutting efficiently.
Related Art
[0003] Conventionally, thread cutting has been performed in various
methods. In many cases, a machine tool including multiple axes has
been used for thread cutting by means of coordinated motion of the
multiple axes, for example. Such thread cutting is realized by
lathe-turning machining of a surface of a circular cylindrical work
in a spiral pattern. This lathe-turning machining is repeated on
the surface of the circular cylindrical work. By doing so, a thread
groove 10 having a sufficient depth is finally formed as shown in
FIG. 5 to finish machining of a screw 12 as a whole.
[0004] FIG. 6 shows a state when the lathe-turning machining is
being performed. As shown in FIG. 6, the thread groove 10 is cut
into a work 14 by cutting with a cutting tool 16 several times
along a predetermined path 10a (position of the thread groove 10)
on the work 14. FIG. 6 shows a state immediately after the start,
of the cutting where the thread groove 10 is shallow. By repeating
the cutting many times, the thread groove 10 is formed into a great
depth (see FIG. 5) to finish formation of the screw 12 as a
finished part. As shown in FIG. 6, the path 10a also exists on the
back side of the work 14. In FIG. 6, for the nature of the path
10a, the path 10a is drawn as the same line as the thread groove 10
for the sake of convenience.
[0005] In FIG. 6, the work 14 is attached to a spindle axis 18 and
rotates. The work 14 rotates in a manner indicated by a circular
arrow C drawn as an arrow surrounding the spindle axis 18. A
rotating coordinate axis indicated by the arrow C is called a
C-axis. In other words, the C-axis corresponds to angular
coordinates indicating an angle about the spindle axis.
[0006] The cutting tool 16 moves along the path 10a on the surface
of the rotating work 14 for machining the thread groove 10 by
cutting. To achieve this, the cutting tool 16 is required to move
along a Z-axis (see FIG. 6) as a coordinate axis extending in the
lengthwise direction of the work 14 in synchronization with the
rotation of the work 14 in the C-axis direction. An arrow Z
indicates the direction of a Z coordinate axis (hereinafter called
the Z-axis).
[0007] By such move of the cutting tool 16 in the Z-axis direction,
the thread groove 10 having what is called a spiral pattern is cut
to form the screw 12, as indicated by P2 in FIG. 6. If the cutting
tool 16 moves fast in the Z-axis direction, the thread groove 10
follows a steeper spiral pattern. If the cutting tool 16 moves
slowly in the Z-axis direction, the thread groove 10 follows a
gentler spiral pattern.
[0008] As described above, cutting is performed several times. At
first, the thread groove 10 is formed into a shallow depth. After
repeating the cutting many times, the thread groove 10 is formed
into a greater depth. More specifically, the cutting tool 16 is
controlled in such a manner that, as a result of each cutting, the
cutting tool 16 gradually moves in the direction of an X coordinate
axis (see FIG. 6) perpendicular to the surface of the work 14 for
cutting of the work 14 at a gradually deepened position. An arrow X
indicates the direction of the X coordinate axis (hereinafter
called an X-axis). As a result of such control, formation of the
screw 12 shown in FIG. 5 is finally finished.
[0009] In the foregoing thread cutting, chips are also required to
be shredded properly. To achieve this, various techniques have been
suggested. For example, patent document 1 discloses a numerical
controller having a function of inserting cutting-out motion,
cutting-in motion, or circular motion. The numerical controller
described in patent document 1 is expected to analyze a condition
for motion designated in a program such as cutting-out motion or
cutting-in motion and insert the cutting-out motion or the
cutting-in motion into lathe-turning machining based on a result of
the analysis. This numerical controller is further expected to
analyze a condition for circular motion designated in the program
and insert the circular motion into the lathe-turning machining
based on a result of the analysis. Patent document 1 states that,
as a result, a numerical controller that makes a machine tool
perform lathe-turning machining allowing fragmentation of chips is
realized.
[0010] Patent document 2 discloses a technique relating to a device
for thread cutting by means of a cutting-in process performed
several times. According to this technique, vibration is
superimposed on the movement of a driving axis to determine
different vibration phase shift amounts between the cutting-in
processes. Patent document 2 states that this device allows
fragmentation of chips with vibration by adjusting a vibration
phase properly in each cutting-in process.
[0011] Patent document 3 discloses a technique by which a
cutting-in process is performed by vibrating a blade relatively
toward a radial direction of a work, and a part to be machined by
this cutting-in process partially covers a machined part resulting
from a different cutting-in process. Patent document 3 states that,
with this configuration, chips occurring during cutting are
fragmented.
[0012] Patent Document 1: Japanese Patent No. 5902753 Patent
Document 2: Japanese Patent No. 5851670 Patent Document 3: PCT
International Publication No. WO2016/056526
SUMMARY OF THE INVENTION
[0013] The foregoing technique of patent document 1 allows
insertion of motion such as cutting-out motion or cutting-in
motion. However, these motions are to be made by a cutting tool and
a process synchronized with motion by a work is not performed. More
specifically, according to patent document 1, regarding insertion
of the foregoing motion, a condition for the motion is analyzed,
and the probability of insertion of the motion is determined.
However, this process (vibration) is not synchronized with a
process of thread cutting involving motion by the work.
[0014] The foregoing technique disclosed in patent document 2
includes the technique of adjusting the phase of oscillation
(vibration). However, like in patent document 1, this oscillation
(vibration) is not synchronized with a process of thread cutting
involving motion by a work.
[0015] Patent document 3 mentioned above describes vibration of a
cutting tool toward a radial direction of a work. However, this
vibration is not synchronized with thread cutting involving motion
by the work.
[0016] As described above, the conventional oscillating machining
is riot synchronized completely with thread cutting. Hence, in
principle, it is difficult to shred chips efficiently along one
path.
[0017] The present invention has been made in view of the foregoing
circumstances. The present invention is intended to provide a
numerical controller for a machine tool capable of shredding chips
efficiently along one path by making oscillating motion involving
synchronization between multiple axes and intermittently making
cutting-out motion and cutting-in motion.
[0018] From the foregoing viewpoint, the present inventors have
found that, in order to shred chips occurring during thread
cutting, causing three axes including at least a work rotary axis,
a tool feed axis, and a tool radial direction motion axis to make
oscillating motion involving synchronization between these axes
makes it possible to generate oscillation that matches the thread
cutting. By doing so, the chips can be shredded efficiently along
one path. More specifically, the present invention employs the
following means.
[0019] (1) The present invention provides a controller (controller
100 described later, for example) for a machine tool used for
thread cutting of a work (work 214 described later, for example) as
a target of the thread cutting using multiple axes, comprising: a
movement command generation unit (movement command generation unit
104 described later, for example) that generates a movement command
for the multiple axes; an oscillation command generation unit (arc
command generation unit 102 described later, for example) that
generates an oscillation command for causing three axes including
at least a work rotary axis (spindle axis 218 described later, for
example), a tool feed axis (Z-axis described later, for example),
and a radial direction motion axis (X-axis described later, for
example) to make oscillating motion involving synchronization
between the three axes including at least the work rotary axis, the
tool feed axis, and the radial direction motion axis, the
oscillation command being for causing a cutting tool (cutting tool
216 described later, for example) for the thread cutting of the
work to make motion of departing from the work while making
cutting-out motion on the work and make cutting-in motion on the
work intermittently; and an adder (adder 106 described later, for
example) that adds the movement command and the oscillation command
and outputs a total movement command (speed command described
later, for example) resulting from the addition, wherein the total
movement command is output to the machine tool.
[0020] (2) In the controller for the machine tool described in (1),
the oscillating motion may be arc motion, and the oscillation
command may be an arc command.
[0021] (3) In the controller for the machine tool described in (1)
or (2), the oscillation command generation unit may generate the
oscillation command for making the intermittent motions at a
predetermined cycle.
[0022] (4) In the controller for the machine tool described in (3),
the predetermined cycle may be synchronized with the work rotary
axis.
[0023] (5) In the controller for the machine tool described in (3),
the predetermined cycle may be a set optional temporal cycle.
[0024] (6) in the controller for the machine tool described in (3),
the predetermined cycle may be defined by an external signal.
[0025] According to the present invention, chips can be shredded
efficiently along one path by making oscillating motion during
thread cutting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a functional block diagram showing the
configuration of a controller 100 of an embodiment;
[0027] FIG. 2 shows oscillating motion (arc motion) involving
synchronization between axes caused to be made by the controller
100 of the embodiment;
[0028] FIG. 3 is an enlarged view of an area A of FIG. 2;
[0029] FIG. 4 shows the oscillating motion (arc motion) involving
the synchronization between the axes viewed from an arrow D of FIG.
3;
[0030] FIG. 5 shows the appearance of a screw formed by thread
cutting; and
[0031] FIG. 6 shows a state when the thread cutting is being
performed for forming the screw.
DETAILED DESCRIPTION OF THE INVENTION
[0032] An embodiment of the present invention will be described
below based on the drawings.
[0033] FIG. 1 is a functional block diagram showing the
configuration of a controller 100 for a machine tool according to
the embodiment. As shown in FIG. 1, the controller 100 includes an
arc command generation unit 102, a movement command generation unit
104, an adder 106, and a control unit 108. These structures of the
controller 100 may be configured using programs describing the
respective motions of these structures and a CPU to execute these
programs. The controller 100 may be configured as a computer. A CPU
in this computer may execute programs describing the respective
functions of the structures of the controller 100 to realize the
structures.
[0034] The arc command generation unit 102 receives arc motion
setting from outside to generate an oscillation command to be added
to a movement command. The arc motion setting is data containing
setting of arc motion in the oscillation command to be given to the
controller 100 by an operator. For example, the arc motion setting
may be data about the arc motion setting input by the operator
through a keyboard or a touch panel. This arc motion setting may be
parameters including the frequency (cycle) of an arc constituting
oscillation, the amplitude of each axis, etc. After receiving these
parameters, the arc command generation unit 102 generates an
oscillation command (arc command) for arc motion based on the
received parameters. The arc motion mentioned herein may be motion
along a circular arc or may include an elliptical arc.
[0035] The arc command generation unit 102 can be configured using
a program describing the foregoing motion, a CPU to execute the
program, and an input interface (keyboard, for example) for input
of the arc motion setting.
[0036] The embodiment is characterized in that oscillating motion
in an oscillation command can be given as a command for arc motion.
Thus, this oscillation command will be called an arc command for
the sake of convenience. To generate an oscillation command as an
arc command, this oscillation command is preferably given as a
command for oscillation involving synchronization between multiple
axes. By generating such oscillation involving synchronization
between the axes, resultant total oscillation can be oscillation
following an arc-like pattern, for example. By doing so, the
oscillation command can function as the arc command. Specific
oscillating motion made in response to the oscillation command as
the arc command will be described in detail later.
[0037] The movement command generation unit 104 generates a
movement command for each axis for thread cutting of a work, for
example. Such generation of a movement command for each axis based
on a predetermined machining program has also been done by a
conventional controller. For example, a movement command for each
axis for thread cutting has already been described by referring to
FIG. 6.
[0038] The adder 106 adds the foregoing movement command and arc
command (oscillation command), and subtracts a position feedback
value from a result of the addition. The calculated positional
deviation is output to a motor 120. Adding the arc command to the
movement command makes it possible to apply oscillation to motion
by each axis. Further, subtracting the position feedback value can
realize what is called position feedback control.
[0039] The control unit 108 generates a command for driving the
motor 120 in response to the input positional deviation and outputs
the generated command to the motor 120. Based on this command, the
motor 120 for a cutting tool is driven to move the cutting tool
relative to the work.
[0040] This command (for each axis) is supplied to the motor 120.
Each axis of the machine tool makes motion such as that described
by referring to FIG. 6 to perform thread cutting. The embodiment is
characterized in that, in this thread cutting, an oscillation
command is applied as an arc command to each axis. In the
embodiment, the oscillation commands for the axes are synchronized
to become the arc command.
[0041] FIG. 2 shows motion responsive to the arc command forming
the characteristic matter of the embodiment. Like FIG. 6, FIG. 2
shows a state when thread cutting is being performed. As
lathe-turning machining proceeds, formation of the screw 12 shown
in FIG. 5 is finally finished. As shown in FIG. 2, in the thread
cutting of the embodiment, a work 214 is also attached to a spindle
axis 218 and rotates. The coordinates of this rotation are
indicated as a C-axis. Like in FIG. 6, an arrow C of FIG. 2 shows
this C-axis and, the C-axis corresponds to angular coordinates
indicating a rotation angle.
[0042] An axis parallel to the lengthwise direction of the work 214
is a Z-axis. An arrow Z of FIG. 2 shows this Z-axis. A cutting tool
216 moves along the Z-axis. By doing so, a spiral thread groove 210
is cut gradually into a surface of the work 214. At this time, a
speed command output from the controller 100 is to make motion
along the C-axis and motion along the Z-axis in synchronization
with each other so that the thread groove 210 can be cut into a
spiral pattern. One of the characteristics of the embodiment is
that oscillation along the C-axis and oscillation along the Z-axis
are synchronized with each other. This makes it possible to apply
oscillation along the thread groove 210 cut using the cutting tool
216 in response to the speed command, as indicated by P1 in FIG. 2.
As a result, chips can be shredded along the thread groove 210.
[0043] In some conventional cases, oscillation is applied
independently to each axis. In such cases, the oscillation is not
always applied along the thread groove 210, causing a likelihood
that chips will not be shredded efficiently. By contrast, in the
embodiment, oscillation along the C-axis and oscillation along the
Z-axis are synchronized with each other. These oscillating motions
can become oscillation along the thread groove 210 to allow
efficient shredding of chips. As described above, in the
embodiment, the arc command generation unit 102 generates an arc
command involving synchronization between the axes. This allows the
cutting tool 216 to make motion of departing from the work 214
while making cutting-out motion on the work 214 and make cutting-in
motion on the work 214 intermittently. This achieves more efficient
shredding of chips.
[0044] FIG. 3 is an enlarged view of an area A at a tip portion of
the cutting tool 216. In the area A, the C-axis is a coordinate
axis extending in a direction substantially perpendicular to the
drawing. The X-axis and the Z-axis extend in their directions
similar to those of FIG. 2. As shown in FIG. 3, in response to a
speed command for the X-axis, the cutting tool 216 further makes
motion along the X-axis. This motion is synchronized with motion
along the C-axis and motion along the Z-axis to realize thread
cutting, as has already been described by referring to FIG. 6, etc.
Each time the work 214 is cut with the cutting tool 216, the
cutting tool 216 moves in a depth direction of the X-axis direction
to cut the thread groove 210 gradually more deeply. The thread
groove 210 is shallow in the state of FIG. 3. As the cutting
proceeds, the thread groove 210 becomes deeper and deeper to be
finally cut into a depth indicated by B. In FIGS. 2 and 3, an arrow
X indicates the X-axis. Oscillation in the X-axis direction is
generated by cutting-in and cutting-out. The cutting-in means
oscillation is applied in a direction in which the cutting tool 216
gets closer to the work 214. The cutting-out means oscillation is
applied in a direction in which the cutting tool 216 gets farther
away from the work 214. Intermittently making the cutting-out
motion and the cutting-in motion in this way allows shredding of
chips occurring from the work 214.
[0045] The embodiment is characterized in that oscillation that
involves synchronization between the C-axis and the Z-axis, and
further with the X-axis is used. As a result of this
synchronization, it becomes possible to lift the cutting tool 216
and then make cutting-in motion again with the cutting tool 216
from a previous position. This allows efficient shredding of
chips.
[0046] As described above, in the embodiment, cutting-out motion
and cutting-in motion are made intermittently by oscillating motion
involving synchronization between the foregoing three axes. The
axes mentioned herein may be various types of axes. For example,
the axes may include work rotary axis (the spindle axis of the
embodiment corresponds to a preferred example of the work rotary
axis) or a tool feed axis (the Z-axis of the embodiment corresponds
to a preferred example of the tool feed axis). Further, one of the
axes to be used may be an axis for oscillation involving
synchronization with radial direction motion (motion in the X-axis
direction of the embodiment corresponds to a preferred example of
radial direction motion).
[0047] FIG. 4 shows a view taken from the direction of an arrow D
of FIG. 3. As this view is taken from the arrow D, the Z-axis is an
axis extending in a direction perpendicular to the drawing instead
of the C-axis. The C-axis is a rotating coordinate axis, so it
should correctly be a coordinate axis extending in an arc-like
pattern. However, in a narrow range such as the area A of FIG. 2,
the C-axis can be approximated to substantially linear coordinates,
as shown in FIG. 4.
[0048] As shown in FIG. 4, oscillating motion on the C-axis and
oscillating motion on the X-axis of the embodiment are synchronized
with each other. By doing so, as shown in FIG. 4, the tip portion
of the cutting tool 216 moves in the C-axis direction and the
Z-axis direction while making oscillating motion in an arc-like
pattern for cutting of the work 214. As a result, the cutting tool
216 becomes capable of departing from the work 214 to allow
shredding (also called fragmentation) of chips. In FIG. 4, motion
with the tip of the cutting tool 216 is drawn conceptually as a
circle. Meanwhile, the cutting tool 216 proceeds in a machining
direction while rotating in an arc-like pattern, so that the
cutting tool 216 actually follows a more complicated path.
[0049] As described above, the embodiment is characterized in that
oscillations at least along the three axes (X-axis, Z-axis, and
C-axis) are synchronized with each other. This achieves a first
result that the cutting tool 216 is allowed to make motion in an
arc-like pattern to be allowed to depart from the work 214. A
second result is that a direction of machining on a work (thread
cutting, for example) and a direction of oscillation can match each
other, so that the oscillation can be generated along the thread
groove 210, for example.
[0050] Thus, machining, or what is called finishing, becomes
unnecessary in some cases. This allows so-called one-path machining
to achieve a process unlikely to be influenced by various machining
conditions. By eliminating the need of what is called finishing, it
becomes possible to realize a more efficient machining process.
Referring to the foregoing technique of patent document 2, for
example, this technique always requires finishing (machining
process that is not oscillation) as a final process. Thus, the
embodiment can contribute to the shortening of machining time.
[0051] In the embodiment, to establish synchronization between
oscillations, oscillation frequencies at the corresponding axes are
required to match each other. This match between the frequencies
(cycles) achieves synchronization. If the amplitudes or phases of
oscillation waveforms at the corresponding axes differ from each
other, an arc followed by the cutting tool 216 generally becomes an
elliptical arc. Adjusting the amplitudes or phases of the
oscillations at the corresponding axes makes it possible to make
the cutting tool 216 follow various types of arcs. In the
embodiment, these oscillations are synchronized with each other at
least at the three axes to allow generation of oscillation along a
machining direction.
[0052] As described above, in the embodiment, the cutting tool 216
can make motion of departing from the work 214 while making
cutting-out motion on the work 214 and make cutting-in motion on
the work 214 intermittently. A cycle of these intermittent motions
can be determined in various ways. For example, a cycle of the
intermittent motions can be a cycle synchronized with a work rotary
axis such as the spindle axis 218. As another example, this cycle
can be an optional temporal cycle set in advance. As a different
example, this cycle may be a cycle defined by an external signal.
In this case, the external signal may be a clock signal indicating
the cycle, or the external signal may be supplied as data
indicating the cycle.
[0053] While the embodiment of the present invention has been
described in detail above, the foregoing embodiment merely shows
specific examples in implementing the present invention. The
technical scope of the present invention should not be limited to
the foregoing embodiment. Various changes are applicable to the
present invention within a range not deviating from the substance
of the invention. All those changes are also included within the
technical scope of the present invention.
[0054] In the example described in the foregoing embodiment, for
example, the spindle axis 218 is an axis about which the work 214
rotates. Alternatively, the spindle axis may be configured as an
axis about which the cutting tool 216 rotates. In this case, a
similar process may also be performed using the rotation of the
spindle axis. More specifically, the spindle axis may function not
only as a work rotary axis but also as a tool rotary axis.
[0055] In the foregoing embodiment, three axes are synchronized
with each other. However, four or more axes may be synchronized
with each other. The foregoing embodiment has been described with
the assumption that oscillation assumes a sine wave, for example.
Meanwhile, any waveform is applicable as long as it is a cyclic
waveform and a frequency (cycle) can be defined in this waveform.
For example, the present invention is applicable to a case where a
waveform is a rectangular wave or a triangular wave. In such cases,
a pattern to be followed by the tip of the cutting tool 216 is not
always a circle or an arc but may be a triangle or a rectangle.
EXPLANATION OF REFERENCE NUMERALS
[0056] 10, 10a, 10b, 210 Thread groove [0057] 12 Screw [0058] 14,
214 Work [0059] 16, 216 Cutting tool [0060] 18, 218 Spindle axis
[0061] 100 Controller [0062] 102 Arc command generation unit [0063]
104 Movement command generation unit [0064] 106 Adder [0065] 108
Control unit [0066] 120 motor [0067] A Area [0068] B Thread groove
(finished state) [0069] C C-axis [0070] D Arrow [0071] X X-axis
[0072] Z Z-axis
* * * * *